This invention relates to thermoluminescent dosimeters and more particularly to tissue equivalent dosimeters which exhibit emission spectra lying in the near ultra-violet region and have high sensitivities to X, gamma and neutron radiations.
The thermoluminescent dosimeter is often employed for measuring an absorbed radiation dose of tissue. Accordingly, it is required that an effective atomic number of the dosimeter, Z.sub.E, be as near as possible to that of tissue. It is generally known that a lithium borate is one of the thermoluminescent materials having nearest Z.sub.E value to that of tissue. Two lithium borate phosphors have been reported and to accomplish the tissue equivalent dosimetry. One of them is manganese-activated lithium tetraborate, and other is silver-activated one. The thermoluminescence emission spectra of both phosphors, however, do not exist in the near ultra-violet region (300 to 500 m.mu.) where widely used photomultiplier tubes show maximum response, the former existing at about 600 m.mu. and the latter at about 290 m.mu.. This causes a loss of optical efficiency in detecting thermoluminescence by the photomultiplier tube, and results in low sensitivity of both phosphos to radiation. Further, lower detection limits of the phosphors are 50 mR and more, and therefore these phosphors are not suitable for application to measurement of a low level radiation dose.